If someone is sleepwalking, they are walking around while they are asleep. Sleepwalking happens when a person is not fully asleep but not quite awake( 清醒的 ). Usually we move from our deepest levels( 层面 ) of sleep to a lighter level and stay there. Sleepwalkers come right up to wake levels but do not fully awaken. It is at this time that they get up and walk. The longer a person stays in deep sleep, the more time there is for the sleep to be broken. That opens up the possibility( 可能性 ) of being awakened(but not fully) and of sleepwalking. Sleepwalking happens more often among young people than grown­ups because young people usually have more deep sleep. Up to 7% of 5 to 12­year­olds sleepwalk, while only about 2% of grown­ups sleepwalk. We get less deep sleep as we are getting older and the possibility of sleepwalking is also reduced . Sleepwalking may run in families, too. If one of your parents was a sleepwalker, you have about a 50% possibility of also being a sleepwalker.